Low cost solar stills have been produced in the past, in emergency kit form or otherwise, for permitting the transformation of potable water from salt water, particularly sea water. Most of the solar stills in which the solar power is the sole energy source for distilling water have been plagued by high cost, complex construction, high maintenance and insulation costs.
Attempts have been made to produce a relatively simple, low cost solar still which performs adequately, can be stored in a relatively small space and is effective as survival equipment. The still set forth in British Patent No. 1,166,840, is characterised by an inflatable tubular fabric member in ring form having thereon a layer of a liquid solar energy absorbent material. A tent-like canopy of a solar energy transmissive material covers the liquid solar energy absorbent material and is in raised position and separated therefrom for providing an air space therebetween. Means are provided for feeding liquid to the liquid absorbent material by capillary action such that the solar energy transmitted through the canopy, and onto the solar energy absorbent material causes the liquid contained therein to evaporate and to subsequently condense as a distillate on the underside of the canopy, from which it is collected. While the structure of the British patent is fairly effective, the utilization of fabric components and the use of an air tube complicates the structure and makes it relatively expensive.
U.S. Pat. No. 2,848,389, issued Aug. 19, 1958, is directed to a solar still which is relatively simple. It is composed principally of an underlying support formed of insulation material and a vertically upright thin wall receptacle for salt water, resting upon and at least partially surrounded by the insulating material base or support. The structure is completed by a relatively rigid transparent plastic sheet of arcuate form whose open side faces downwardly, and which terminates at the opposite edges in integral, rigid, curved channels and which may be are linked to or integrated with the salt water receptacle centered between the channels and fixed to the insulation material support. In the various embodiments, a relatively rigid transparent sheet is required to be molded into the desired curved shape to produce the arcuate overlying cover and the upwardly facing arcuate channels 3 and 4 to opposite sides thereof and at the lateral edges of the cover sheet. In the system of U.S. Pat. No. 2,848,389, the saline water can be pumped into the salt water receptacle for periodic refilling. The components of the solar still are preferably formed of a substantially rigid, transparent, organic, synthetic resinous polymeric material.
The structures of U.S. Pat. No. 2,848,389, involve rigid molded plastic components which do not lend themselves to forming a compact kit and require the expense of rigid molding with attendant weight problems.
It is therefore a primary object of the present invention to provide a low cost simplified solar still for distilling water which uses a thin film, flexible plastic sheet material, which film sheet material may be in bag form, and which conforms to and is maintained by a wire frame assembly, which functions both to define a moisture condensing surface and to form one or more integral collection troughs and which utilizes a commercially available foam insulation pan for the salt water to be distilled.